    Patent document 1: JP H10-201001 A
A visually impaired pedestrian generally recognizes the presence of a vehicle with an engine sound. Vehicles such as an electric vehicle and a fuel cell electric vehicle that travel with an electric motor do not have an internal-combustion engine. Thus, it is not easy for a visually impaired person to notice the presence of a vehicle having no engine. Similarly, a hybrid vehicle stops an engine during low loaded traveling and travel stopping and does not emit any engine sound during stopping the engine. Therefore, it is not easy for a visually impaired person to notice the presence of a hybrid vehicle during stopping the engine.
In addition, there is recently improved a technology to reduce an engine sound so that the engine sound may not be heard by a pedestrian easily. A visually impaired person may not notice the presence of a vehicle with a quiet engine sound under the influence of street noises.
A visually impaired person may raise a recognition accuracy of recognizing a position in a vehicular back and forth direction by using sound information such as a sound tone of an engine sound or a sound tone of a traveling sound and also by combining a variety of sound information, for instance, (i) combining the engine sound and the traveling sound, or (ii) combining the engine sound and the exhaust sound. In particular, a fine sound tone difference between a sound heard by the left ear and a sound heard by the right ear may be distinguished instantaneously to thereby raise a recognition accuracy of recognizing a position in a vehicular back and forth direction.
For instance, Patent document 1 proposes a technology to generate a notice sound from an in-vehicle dynamic speaker to emit directly an audible sound outward from the vehicle to indicate the presence of the vehicle to an area surrounding the vehicle. The notice sound emitted from the dynamic speaker is audible in an area surrounding a vehicle S as illustrated as a solid line circle β in FIG. 10.
However, a visually impaired person may not easily distinguish a position in the back and forth direction of the vehicle only by the notice sound generated from the above dynamic speaker. The above explanation was made specifically for a visually impaired person as an example. Even a person with a normal eyesight may recognize a position in the back and forth direction of the vehicle unconsciously by the sound information through the ears. Therefore, it may be desirable that even a person with a normal eyesight recognize a position in the back and forth direction of the vehicle using the sound information.